An organic electroluminescence device is an electric element which emits light through the current by an applied voltage. Tang et al. reported an organic electroluminescence device having good characteristics in a treatise [Applied Physics Letters 51, p. 913, 1987]. Further, an organic electroluminescence device using a polymeric material while using a structure of the organic electroluminescence device disclosed in the treatise has also been developed.
The key point of the related art as described above is to allow different organic material layers to share roles for performing processes in which an organic electroluminescence device emits light, that is, charge injection, charge transport, formation of optical exciton and generation of light. Therefore, in recent years, there has been used an organic electroluminescence device including a substrate 1, a first electrode 2, a hole injection layer 3, a hole transporting layer 4, a light emitting layer 5, an electron transporting layer 6, an electron injection layer 7, and a second electrode 8, as illustrated in FIG. 1, or an organic electroluminescence device having a structure subdivided into more layers. Meanwhile, various element manufacturing structures are used in electron injection and transporting layers in order to smoothly move electrons from the second electrode to the light emitting layer.
For example, a metal compound belonging to the alkali group, such as LiF, NaF, and LiQ, is frequently used as a material for the electron injection layer, and an organic material basically having a stable structure when electrons move is frequently used in the electron transporting layer. In order to realize a better element efficiency, as a material for the electron transporting layer, materials having a larger band gap than the exciton energy of a light emitting layer and a deep HOMO Level in order to block holes overflowing from the light emitting layer are frequently used.
In order to improve electron injection characteristics of the electron transporting layer, metals and metal compounds belonging to the alkali group, such as Li, Ca, LiF, and LiQ, may also be used with a material for the electron transporting layer to form a layer.
However, these metals and metal compounds belonging to the alkali group each have a small atomic or molecular weight so that there is room for these metals and metal compounds to easily move in the element, which also adversely affects the service life of the element.